Field
The present invention relates to methods and devices for forming a common datastream from several datastreams based on the Advanced Television Systems Committee (ATSC) standard.
Related Art
The transmission of digital-television signals in the USA and in some other countries—for example, in South Korea—is implemented according to the Advanced Television Systems Committee (ATSC) standard. The digital-television signals in this context are coded according to an MPEG-2-coding algorithm and transferred in data packets without synchronization information to stationary, localized television devices, as known, for example, from WO 2006/094050 A2.
The existing transmitter network for stationary, localized television devices is to be used for the transmission of digital-television signals to mobile telephone devices. Furthermore, the existing receivers of the stationary, localized television devices must still be able to receive the digital-television signals transmitted in the ATSC data packets without upgrading. Accordingly, the useful data for mobile-digital television in addition to the useful data for stationary-digital television must be integrated in ATSC data packets.
FIG. 1 illustrates a data structure of an ATSC transport-stream data packet. Signals are sent to the receivers of stationary-television devices and mobile telephones via the signalization field “Adaptation Field Control”. The Adaptation Field Control field indicates whether the useful-data fields “Stuffing Bytes”, which are designated for useful data of the mobile-digital television and, if required, in the useful data fields “Payload Data”, which are determined at origin of the useful data of the stationary-digital television. If useful data for mobile-digital television are transmitted in the currently-transmitted ATSC data packet, the entire length of the useful data for mobile-digital television can be obtained from the data field “Adaptation Field Length”, and the additional demand for useful data of mobile-digital television required in the useful data field “Payload Data” can be obtained from the data field “Adaptation Field Extension”. In this manner, a receiver of a mobile-telephone device can have access to data fields in the useful-data fields “Stuffing Bytes” and optionally in the useful-data fields “Payload Data” and, at the same time, a receiver of a stationary, localized television device can have access to the data fields in the useful-data fields “Payload Data” of the same ATSC data packet remaining for the transmission of useful data of the stationary-digital television.
In the coding of the mobile-digital television signals—typically with an H.264 encoder—a datastream is formed. The data rate of the datastream is dependent upon the image content to be transmitted at the respective time or upon the dynamic of the image contents to be transmitted—time variation of the image content. Consequently, the maximum-required data rate must be reserved at the output of a respective coder. Since this maximum data rate is required only at given times or phases, the transmission channel between transmitter and receiver is disadvantageously loaded in a comparatively inefficient manner.